Lasers are ubiquitous devices used for testing, measuring, printing, cutting, marking, medical applications, communications, data transmission, semiconductor processing, and many other applications. Many types of lasers have been developed to meet different performance criteria for different applications. Engraving, cutting, marking, printing and many other applications require relatively compact lasers that generate high power output and have beams with a desired shape and energy distribution. Accordingly, equipment containing a source of laser radiation is required by law in most countries to meet certain safety standards in order to protect the user and others from exposure to the laser beam. These safety standards generally classify lasers and laser systems by the amount of laser radiation to which a user could be exposed during normal operation and maintenance. The classifications, as defined by federal and international regulatory agencies, range from class I through class IV, in order of increasing hazard.
Class I laser systems, for example, are designed to ensure that a user has no exposure to laser radiation. All laser radiation is contained within a light-tight enclosure made from one or more materials designed to withstand direct exposure to the unfocused laser beam contained inside the enclosure for an indefinite amount of time. Some examples of class I laser systems include laser printers, CD players, and CD-ROM devices. No safety precautions are needed to operate class I laser systems. Class II laser systems (e.g., laser pointers for presentations, consumer aiming/leveling devices, and range finding equipment) contain visible light, lower power lasers (i.e., less than 1 mW), and class IIIa laser systems (e.g., laser pointers and laser scanners) contain continuous wave, intermediate power lasers (i.e., 1-5 mW). Direct viewing of class II and class IIIa laser beams can be hazardous to a person's eyes, but the human blink reflex is generally expected to provide adequate protection for users of such systems.
On the other hand, class IIIb and class IV laser systems can be hazardous to users and, therefore, a number of different safety measures must be taken when using such systems. For example, class IIIb laser systems (e.g., spectrometers, stereo lithography equipment, and entertainment light show equipment) contain intermediate power lasers (i.e., continuous wave 5-500 mW or pulsed 1-10 J/cm2), and direct viewing of class IIIb laser beams, as well as diffuse reflections of such beams, are hazardous to a person's eyes. Therefore, appropriate safety precautions and proper eye protection are required for users of class IIIb lasers.
Class IV laser systems (e.g., laser surgery equipment, lasers used in research settings, laser drilling, welding and cutting equipment, etc.) contain high-power lasers (i.e., continuous wave greater than 500 mW or pulsed greater than 10 J/cm2). The direct beam and diffuse reflections from class IV lasers are hazardous to both the eyes and skin. Class IV laser systems can also be a fire hazard, depending on the reaction of the target material when struck by the beam. Accordingly, much greater controls are required to ensure the safe operation of class IV laser systems. For example, proper eye protection is required at all times and, depending on the wavelength, skin protection may also be required. In addition, areas in which class IV laser systems are used must be secured to allow the system's owner/operator to restrict access to the laser system since the operator and any bystanders could be exposed to the laser beam. Facilities in which class IV laser systems are operated are required by law (e.g., international, federal, and/or state) to follow certain laser safety protocols. Such protocols can include, for example, training and appointing a laser safety officer to oversee installation and operation of class IV laser systems, operating class IV laser systems in restricted areas with interlocked or secured entrances that shut off the laser whenever any entrance is opened, providing ongoing safety training for all users of class IV laser systems, ensuring proper eye/skin protection is provided for all users of class IV laser systems, and providing regular eye tests for all users of such systems. The owner/operator of a class IV system is also generally responsible for registering the system with the appropriate governmental agency, paying the necessary fees to the agency or appropriate entity, and regular recording of certain operational information. Manufacturers and distributors of class IV laser systems are responsible for informing potential purchasers about the dangers and responsibilities of owning and operating class IV laser systems, and the purchaser is then responsible for implementing and following all of the required safety protocols.
Many class I laser systems used for material processing (e.g., cutting, marking, welding, etc.) contain lasers powerful enough to be classified as class IV; however, the beam is contained in an exterior housing or enclosure configured in such a way that the overall system can be classified as a class I laser system. Accordingly, openings to the housing, such as doors and hatches meant to be opened during normal operation and maintenance, must be redundantly interlocked to ensure that the laser is shut off or the beam is effectively blocked when any of these doors or hatches is opened.
One drawback with such laser systems, however, is that the arrangement of the housing can significantly limit the size of workpieces that can be placed within the system for processing. For example, most class I laser systems that include high-power (e.g., class IV) lasers are configured to only process workpieces that fit entirely within the housing because the interlocks on each door of the housing must remain engaged or otherwise activated to maintain class I operation of the system. In some cases, however, a user can defeat or otherwise deactivate the interlocks on one or more of the doors to allow a portion of an oversized workpiece to be positioned within the housing for processing. In such cases, the user has effectively nullified the laser system's safety features and turned a class I system into a potentially hazardous laser system with no classification. Furthermore, the system's user/operator was not likely informed of the dangers and responsibilities associated with operating a class IV laser system because the laser system was sold or provided as a class I laser system, and manufacturers/resellers of class I systems are not required to provide such information. Although many manufacturers of class I laser systems that include high-power lasers make reasonable efforts to prevent interlocks on the system's housing from being compromised and/or defeated, a significant number of conventional laser systems include safety features that are relatively easy to defeat and, furthermore, many manufacturers turn a blind eye to such issues.